Apparatus for continuous metallization of dielectric strips



I ,Mar ch 3; 1970 r M. A. BRAGUIER 3, 98,

APPARATUS FOR CON TINUOUS METALLIZATION OF DIELECTRIC STRIPS med Dec. 13. 1967 4 Sheets-Sheet 1 mvanrom' Michgl A.IBRAGUIER By 54% 1a ATTORNEY March 3 1970 M. A. BRAGUIER 3,498,259

APPARATUS FOR CONTINUOUS METALLIZATION OF-DIELECTRIC STRIPS Filed Dec. 13, 1967 4 Sheets-Sheet 2 Fig.2

INVENTOR:

Michel A. BRAGUI R ATTO I MArch 1970 MIA. BFIAGUIER I I 3,498,259

APPARATUS FOR CONTINUOUS METALLI ZATION OF DIELECTRIC STRIPS Filed Dec. 13, 1967 4 Sheets-Sheet 5 9 F ff/ 1 1 I w R. x

INVENTOR:

Michel A. BRAGUI By M i f ATTO Y 2 A March 3, 1970 M. A. BRAGUIER APPARATUS FOR CONTINUOUS METALLIZATION OF DIELECTRIC STRIPS Filed Dec. 15, 1967 4 Sheets-Sheet. 4

' mvz-moa: Michel A. BRAjJI R y J'- y ATTO N Q 8 N a v ifllw w mmil Ail wi$llflv g 9 9 Q N E W mm a \m Q% g o o o mh W g Ill vb United States Patent 3,498,259 APPARATUS FOR CONTINUOUS METALLIZATION OF DIELECTRIC STRIPS Michel A. Braguier, 6 Rue de Commaille, 75 Paris, France Filed Dec. 13, 1967, Ser. No. 690,272 Int Cl. C23c 13/08 U.S. Cl. 118-49 4 Claims ABSTRACT OF THE DISCLOSURE Apparatus for continuous vacuum metallization of a strip of insulating material in which the strip passes on cooling rollers, each including: (a) a hollow rotating drum made of thin metal which is a good heat conductor, the cylinder outer surface being polished and the cylinder inside surface being blackened; (b) inside the drum, a nonrotating stationary cylinder made of a thin metal which is a good heat conductor, the casing outer surface being blackened, the casing being flowed through by a fluid coolant; (c) in the casing, a stationary cylinder formed with ducts for supplying and removing the said fluid coolant, the rotatable drum being adapted to rotate freely around the stationary cylinder, and provided with means for directing the metal vapor flow towards selected parts of the cooling roller.

This invention relates to apparatuses for continuous vacuum metallization of one or both surfaces of dielectric strips, more particularly to apparatuses of the kind specified wherein special cooling rollers are used.

Some known apparatuses for continuous vacuum metallization of insulating strips comprise cooling rollers over which the strip passes between its take-off in untreated form and its take-up in treated form and which make the strip temperature low enough for the strip to be metallized without being damaged. For instance, in the case of aluminization of the strip, aluminum vapors have a temperature of approximately 1400 C., but strip temperature should preferably not exceed normal ambient temperature of, say, 25 to 30 C. The cooling rollers are rotating rollers which are flowed through by a cooling fluid and which have a rotating seal which allows a cooling fluid to flow inside the roller but keeps out unwanted an.

The disadvantage of this kind of roller is that the presence of the rotating seal causes the roller to have an appreciable resistive torque, and so the roller must be driven and its speed must be dependent upon and follow the speed of the strip movement.

It is a main object of this invention to provide a vacuum metallization apparatus comprising one or more cooling rollers which are free from these disadvantages and which can therefore provide very satisfactory cooling yet offer a very reduced resistive torque.

To this end, the rollers of the metallization apparatus according to the invention mainly comprise: (a) a hollow rotating cylinder made of thin metal which is a good heat conductor, the cylinder outer surface being polished and the cylinder inside surface being oxidized; (b) inside the cylinder, a non-rotating stationary casing made of a thin metal which is a good heat conductor, the easing outer surface being oxidized, the casing being flowed through by a fluid coolant; (c) in the casing, a stationary cylinder formed with the required ducts for supplying and removing the fluid coolant, the rotatable cylinder being adapted to rotate freely around the last-mentioned stationary cylinder.

Consequently, and as will be seen in greater detail hereinafter, the unreflected fraction of the incident heat due to metallization can be transmitted integrally and rapidly from the cylinder to the casing by radiation between two surfaces which can be likened to black bodies, and so the temperature of the outer cylinder of the roller can be controlled very simply just by acting on the inlet temperature of the fluid coolant.

Another aim of the invention is to bind the edges of the or each metallized strip.

Other features and advantages of the invention will become apparent from the following description of a non-limitative embodiment, reference being made to the accompanying drawings wherein:

FIGURE 1 is a perspective view, seen from the front, of the metallizing apparatus according to the invention;

FIGS. 2 and 3 are diagrammatic views, for both-surface and single-surface metallization of the strip respectively showing the path of the strip in the apparatus;

FIG. 4 is a view in axial section of a cooling roller of the apparatus;

FIG. 5 is a perspective view of the mask associated with the cooling roller, and

FIG. 6 shows a pattern of strip metallized by the apparatus according to the invention.

Referring to FIG. 1, a continuous metallizing apparatus is received in a circular box 1 whose front surface 2 forms a cover and which can be closed in vacuumtight manner thanks to the presence of an appropriate plastics head 3. The box 1 can be exhausted by means which are not shown.

A crucible 4 can be electrically heated by a winding 5 of resistive wire. An aluminum wire 6 wound on a reel 7- is directed towards the crucible 4 through the agency of a guide tube 8 and a drive facility 9 comprising a drive shaft 10. Upon leaving the tube 8 the wire 6 melts and drops into crucible 4 in which it is vaporized. A deflector 11 cooled by a flowing fluid coolant (the flow tubes are not shown) directs the aluminum vapor towards the cooling rollers 12, 13.

A plastic strip 30 which it is required to coat and which can take the form, for instance, of substances known under the names of Mylar or Polycarbonate unwinds from a take-off reel 14, then goes over the cooling rollers 12, 13 and over any other rollers, finally to be taken up on a take-up reel 15. Not all the rollers have references, since some of them are merely deflecting idler rollers or serve merely to turn round the surface to be metallized. Springs 20, 21 bias respective rollers 16, 18 disposed at the ends of respective arms 17, 19 against the take-off winding 14 and take up winding 15 respectively to obviate creasing during the unwinding and winding-on of the strip. Rollers 22, 23 measure the resistance of the metallized layer on the surface 31, and rollers 24, 25 measure the resistance of the metallized layer on surface 32, of strip 30. Rollers 26, 27 are drive rollers. A rubber roller 28 is connected to a tachymeter dynamo for controlling the drive speed.

As can be seen in FIG. 2, the surface 31 is on the outside when the strip goes over the cooling roller 12, and the surface 32 is on the outside when the strip goes over the cooling roller 13, whereas in FIG. 3 the surface 32 is on the outside when the strip goes over both of the rollers 12, 13. Clearly, therefore, by changing the path of the strip 30, the apparatus can be used to metallize either both the surfaces of the strip or one surface thereof. Two stationary screens 29, 29' provide protection against the metal vapor for all rollers other than the cooling rollers and for the strip too except at the place where the same' goes over the cooling rollers.

Referring now to FIG. 4, each cooling roller takes the form of a thin hollow aluminum cylinder 33 which is polished on its outside surface and oxidized on its inside 3 surface. The cylinder 33 is formed at both ends with cylindrical recesses 34 receiving two identical aluminumoxide end plates 35, 36 formed coaxially with cylindrical recesses 37 receiving antifriction bearings 38, 39 mounted on a steel cylinder 40 kept horizontal by base 48 of box 1. Preferably, the bearings 38, 39 are lubricated with Teflon grease.

A stationary cylindrical casing 41 of reduced thickness is secured coaxially to the cylinder 40, e.g., by grazing, and takes up almost all the free space in the cylinder 33 between the end plates 35, 36; the casing 41 is made of copper with the outer surface oxidized. The casing 41 is filled with a moving fluid refrigerant 42, for instance,

water. The fluid 42 flows through passages contrived in the cylinder 40, namely a cold fluid supply passage 43, whose exit orifice is flush with the surface of the cylinder 40, and a hot fluid removal passage 44, which continues radially in the form of a tube 45 to near the cylindrical wall of the casing 41.

When the enclosure 1 in which the rollers 12, 13 are disposed is exhausted, the air between the cylinder 33 and the casing 41 is removed through a number of orifices, as 46, 47, in the end plates 35, 36.

Of course, the hottest part of the apparatus hereinbefore described is the system formed by the cylinder 33 and end plates 35, 36. This system absorbs only a fraction of the incident heat due to the metallization, since the cylinder 33 has a polished outer surface and extends completely around the coldest parti.e., the casing 41 which the continuously flowing fluid coolant 42 maintains at a predetermined temperature.

The inner surface of the cylinder 33 and the outer surface of the casing 41, since they are oxidized, can be likened substantially to two black bodies. Also, the metals-aluminum and copper-used for the cylinder 33 and casing 41, respectively, are good heat conductors and of reduced thickness and therefore have a low heat imepdance. Furthermore, the medium between the cylinder 33 and the casing 41 is substantially nonabsorbent. Consequently, the cylinder 33 rapidly transfers all the heat which it absorbs to the casing 41 by radiation; this transfer is governed by Stefans law, which simplifies for the case of two black bodies at very similar temperatures and can be represented by the relationship:

in which P denotes the heat (in watts) transmitted by radiation from the cylinder 33 to the casing 41; S denotes the area of the casing 41 in square meters; denotes Stefan constant 5.7 w./m. degrees K T denotes the temperature of the casing 41 in K.; and AT denotes the temperature difference between the cylinder 33 and the casing 41.

When the roller receives heat radiation, most of the incident heat is reflected by the outer polished surface of the roller. The nonreflected fraction, called P, is transmitted entirely and rapidly to the casingi.e., to the fluid coolant, which removes such fraction. A temperature difference AT is produced and maintained between the cylinder and the casing, the value .of AT resulting from Formula 1; controlling the temperature at which the fluid coolant reaches the casing controls the cylinder outer temperature.

EXAMPLE A roller according to the invention was constructed as follows:

Cylinder 33 of aluminum, polished outside and oxidized Length 150 4 Casing 41 of copper oxidized outside- Outer diameter 148 Inner diameter -1 144 Wall thickness 2 Length The fluid coolant was water.

The bottom generatrix of the roller was mm. vertically above the level of the exposed surface of a melted aluminum bath at I400 C., with a radiating area of 5 cm.

The plastic strip .of Polycarbonate 6n thick rested on the roller and moved at a constant speed of 0.5 m./sec.; it was coated with a uniform layer of aluminum having a square resistance of 3 ohms. The term square resist ancedenotes the resistance of a layer Whose length is equal to its width; the square resistance is inversely proportional to layer thickness.

Consequently, once steady conditions had been reached the heat transmitted to the roller was approximately 120 watts and the temperature difference between the roller and the casing stabilized at 15 C., corresponding to 1 C. per 8 watts of incident heat. To keep the roller outer surface at +25 C., the cooling water entered the roller at 10 C.

A removable mask 49, for instance of the kind shown in FIG. 5, can be placed around each cooling roller 12, 13. In general shape the mask 49 resembles a cylindrical sector or a half-cylinder and comprises a frame formed by two semicircular rods 50, 51 and by two straight rods 52, 53 which itnerconnect the ends of the semicircular rods 50, 51. The ends of the semicircular rods 50, 51 are pierced with apertures 54 so that the mask 49' can be threaded on rods 68 which are perpendicular to and secured to the base 48 of the box 1. Each of the straight rods 52, 53 is formed with a longitudinal slot 55 in which slide blocks 56 terminating in semicircular rods 57, 57 can move. The slide blocks 56 can be located and locked by screws 58. Plates 60, 60 which in shape resemble a sector of cylindrical surface and which are of predetermined width are secured laterally to semicircular rods, as 50, 51, by screws 59.

FIG. 6 shows the form of metallized layer produced on the strop 30 in the case in which the mask 49 is devised as shown in FIG. 5. There are three metallized strips 6163 bordered and separated by edges .or selvages 64, 65, 66, 67. The eges 64, 67 are due to the plates 60, 60. The width of the metallized strips and the spacings therebetween are the result of appropriate positioning of the rods 57, 57' and of the width chosen for the plates 60, 60'.

It must be well understood that the metal of the drum and easing must be selected so as to take by metallization a mat black surface and the operation of the drum depends to a fairly large extent on the colors of the opposed surfaces. Copper oxide is capable of providing an intensely black nonreflecting surface. As for aluminium, the inner surface of the drum must be treated so as to obtain a mat black surface (for instance by anodic oxidation) and not a white mat surface.

What I claim:

1. An apparatus for continuous vacuum metallization of a strip of insulating material comprising means for vaporizing a metal, a take-off reel and a take-up reel, and at least one cooling roller over which the strip passes, including; (a) a hollow rotating cylinder made of thin metal which is a good heat conductor, the cylinder outer surface being polished and the cylinder inside surface being oxidized to effect a black-body type surface; (b) inside the cylinder, a nonrotating stationary casing made of a thin metal which is a good heat conductor, the casing outer surface being oxidized to effect a black-body type rotatable cylinder being adapted to rotate freely around the last-mentioned stationary cylinder, and means for directing the vapor flow towards selected parts of said cooling roller.

2. An apparatus for continuous vacuum metallization of both surfaces of an insulating strip as set forth in claim 1, and comprising two cooling rollers over which the strip runs, one of the strip surfaces being outside the first roller and the other strip surface being outside the second roller.

3. An apparatus for continuous vacuum metallization of an insulating strip as set forth in claim 1 wherein the rotating hollow cylinder is made of aluminum and the nonrotating stationary casing is made of copper.

4. An apparatus for continuous vacuum metallization of an insulating strip as set forth in claim 1 wherein the means for directing the vapor flow towards selected parts of the cooling roller comprise a frame having the form of a cylindrical sector coaxial to the cooling roller and comprising two terminal bars in the form of a circle sector and two straight bars interconnecting the ends of the circlesector bars in pairs, slots forming slideways in said straight bars, intermediate circle-sector rods terminating in slide blocks sliding in the slideway slots, and plates in the form of a cylindrical sector connected laterally to the intermediate rods.

References Cited UNITED STATES PATENTS 1,708,935 4/ 1929 Christopher. 2,877,140 3/1959 Olstad 11869 X 2,975,753 3/1961 Hayes 11849 3,018,397 Bronco et a1 165-133 X 3,044,438 7/1962 Osswald et al. 118-49.1 3,183,563 5/1965 Smith 11849.1 3,241,519 3/1966 Lloyd 11849- 3,381,660 5/1968 Bassan 118-49 3,397,672 8/1968 Dykeman et al. 11849.5 X

FOREIGN PATENTS 350,471 6/ 1931 Great Britain.

MORRIS KAPLAN, Primary Examiner US. Cl. X.R. 

